STARCH-SUBSTANCE, AND THE STRUCTURE, ETC., OF THE STARCH-GRAIN. 47 



structure. The lines of lamellation of such swollen grains are not regular but zig-zag, 

 and the presence of these small projections gives rise to the illusory honey-combed appear- 

 ance. Starch-grains from the potato likewise did not show a honey-comb structure in 

 the fresh condition, and in only very few of the grains could such a formation be seen after 

 swelling. Here also the appearance of such a texture is illusory, and merely an optical 

 effect due to the zig-zag lamella?. In a few instances traces of the honey-comb structure 

 could be seen in Carina indica. This form of starch is very suitable for such an investiga- 

 tion on account of the large and prominent lamella;. Grains from wheat did not show a 

 honejf-comb peculiarity, either in the fresh or swollen condition. Puriewitsch therefore 

 declines to accept Biitschli's view of the peculiar honey-combed structure of starch. 



An important contribution to the hterature of starch, covering quite a broad field 

 of investigation, was published in 1895 by Meyer (Untersuchungen uber die Starkekorner. 

 Wesen und Lebensgeschichte der Starkekorner der hoheren Pflanzen, Jena, 1895, mit 9 

 Tafeln und 99 in den Text gedruckten Abbildungen, S. 318). Meyer notes that even at 

 this time our knowledge of the chemical substances which compose the starch-grain, and 

 of the products of decomposition, is very meager in spite of the enormous amount of work 

 that has been done. Meyer concluded from his investigations that in ordinary starch- 

 grains only amylose and small amounts of amylodextrin are present. The former he states 

 is present in two forms, one of which dissolves in water at 100°, but the other not. The 

 difference, he assumes, is due to the existence in starch-grains of anhydrous crystals, of 

 crystals which contain water, of crystals that are soluble with difficulty in water, and of 

 crystals easUy soluble in water. The easily soluble modification of amylose he terms 

 /3-amylose, and the difficultly soluble he terms a-amylose. 



a-Amylose. — Just as there is a dextrose anhydride, Meyer writes, which in cold water 

 does not take up water of crystallization directly, there also appears to be amylose anhy- 

 dride which upon boiling in water passes into a hydrate very slowly, and this fact has partly 

 given rise to the conception of the so-called starch-cellulose. The term starch-cellulose, 

 he notes, has been applied to very different substances — to mixtures of amylodextrin with 

 a-amylose, of dissolved /3-amylose and a-amylose, of dissolved /3-amylose and nitrogenous 

 and fatty impurities, and to amylodextrin in an almost pure state. Meyer states that he 

 concluded in 1886 that the skeletons of starch formed during acid and salivary digestion 

 do not consist of a substance that is contained originally in the starch-grain, but of amylo- 

 dextrin, a transformation product of amylose. Later researches, however, showed him 

 that this conclusion was not strictly correct, and that acid skeletons are of variable 

 composition, and consist, depending upon the length of time the acid acts, of a mLxture of 

 /3-amylose, a-amylose, and amylodextrin; or of a-amylose and amylodextrin; or of amylo- 

 dextrin alone. That amylodextrin alone is left after acid action for a sufficient time was 

 proved, he records, by an experiment in which a 12 per cent hydrochloric acid solution 

 was allowed to act on potato starch for eight and one-half years, at the end of which time 

 the skeletons contained only amylodextrin. It is different, he records, with the saliva- 

 skeletons, which, if the amylose hydrate has been dissolved out of the grains, consist of 

 a mixture of amylodextrin and a-amylose. a-amylose he obtained by treating starch-paste 

 with malt extract, or by the action of hot dilute hydrochloric acid on whole starch-grains. 

 He found that when starch-grains are treated for a short time with saliva or with a cold 

 dilute acid, and the skeletons extracted with hot water, there remained a residue wliich 

 differed in its properties from other substances of the grains in that it was insoluble in 

 hot water, and was colored red instead of blue with Lugol's solution. 



Meyer beUeves it probable that a-amylose is to some extent present in starch-grains 

 from the beginning in crystallized forms which offer great resistance to boiling water, 

 and to the penetration of iodine into the small crystals. That a-amylose is already con- 

 tained in the intact grains is shown, he states, in the following experiment : If arrowroot 



